Adrian Fox. Carrot viruses

Transcription

1 Adrian Fox Carrot viruses

2 Carrot viruses Alfalfa mosaic alfamovirus Arabis mosaic nepovirus Beet pseudo-yellows (?) closterovirus Carrot latent nucleorhabdovirus Carrot mosaic (?) potyvirus Carrot mottle mimic umbravirus Carrot mottle umbravirus Carrot red leaf luteovirus Carrot red leaf associated viral RNA Carrot temperate 1 alphacryptovirus Carrot temperate 2 betacryptovirus Carrot temperate 3 alphacryptovirus Carrot temperate 4 alphacryptovirus Carrot thin leaf potyvirus Carrot yellow leaf (?) closterovirus Cassava green mottle nepovirus Celery mosaic potyvirus Celery yellow net (?) virus Clover yellow vein potyvirus Coriander feathery red vein nucleorhabdovirus Cucumber mosaic cucumovirus Galinsoga mosaic carmovirus Heracleum latent trichovirus Lettuce infectious yellows (?) closterovirus Oat blue dwarf marafivirus Okra mosaic tymovirus Parsnip mosaic potyvirus Parsnip yellow fleck sequivirus Poplar mosaic carlavirus Potato black ringspot nepovirus Strawberry latent ringspot (?) nepovirus Tobacco ringspot nepovirus Tomato black ring nepovirus Tulip X potexvirus

3 Parsnip yellow fleck virus (PYFV) PYFV carrot isolates to Cow Parsley reservoirs Requires Anthriscus yellows virus (AYV) for transmission C/CP Results from FV382 suggest this virus is not involved in internal browning Carrot is not susceptible to AYV Direct carrot to carrot H/P transmission not a factor Work carried out under HDC/HortLINK FV228

4 Carrot red leaf virus (CtRLV) Carrot red leaf virus needed for transmission of CMD viruses Most carrot isolates form a distinct carrot group Weed group isolates from: Cow parsley, Hogweed, Pignut, Sweet Ciceley, Wild Parsnip, Hemlock, Rough Chervil, Wild Carrot and Carrot (limited) Carrot to carrot major factor in CMD Carrot Weed Work carried out at Warwick Crop Centre under Defra IF0188

5 Simplifying the complex... Salix spp. Or Umbelliferous weeds Cow Parsley? AYV + PYFV Aphids on winter host Aphids Migrate Pick up Virus Transmit to Carrot Carrots under straw?? CtRLV (CMoV) (CtRLVaRNA) Carrots?

6 Viral browning of carrots (HDC FV382a) Conventional PCR of affected & unaffected carrots showed no association with expected viruses Stocks of carrots rejected due to the presence of internal necrosis linked to viruses real-time PCR demonstrated a strong association between CYLV and necrosis, suggesting that removal of this virus would reduce necrosis by 96% samples positive affected unaffected PYFV CRLV CRLaV CMoV CYLV Negative Virus MiSeq sequencing identified Carrot yellow leaf virus in necrotic samples. Sequencing also detected a Closterovirus (CtCV) and a Torradovirus (CaTV) plus 5 other viruses which were new to science.

7 2014: tracking down the viruses

8 2014 : Wild hosts of new viruses (2012 weed samples) Species No. of fields sampled No. Of Samples CaRLV CMoV CaRLaVRNA PYFV CYLV CtCV CaTV Hogweed (1.7%) 1 (1.7%) 1 (1.7%) Cow Parsley 7 27 (25.9%) (11.1%) (29.6%) Hemlock 1 1 Rough Chervil (33%) Total CaRLV, CMoV & CaRLV = Carrot Motley Dwarf PYFV = Parsnip yellow fleck virus CYLV = Carrot yellow leaf virus (NEW - linked to root necrosis) CtCV = Carrot closterovirus (NEW similar to CYLV) CaTV = Carrot toradovirus (NEW unknown incidence and impact)

9 2014 Field sampling (HDC FV 382b + Defra Funding) Samples from carrot crops 100m x 100m blocks Sampled in season to assess infection levels and assess foliar symptom development; Roots sampled at end of season to assess levels of necrosis against infection To be repeated on a broad geographic basis in 2015

10 Comparative virus health of 3 fields (N.Yorks) Positive Negative Strensall Sand Hutton Sutton on the Forest

11 Relative virus incidence between 3 fields (N. Yorks)

12 High Roans Field Field Margin and Road N Hedgerow CYLV 23% CTV 25% DUAL 9%

13 Ongoing work Transmission studies and Koch s postulates (HDC) Incidence of carrot viruses (HDC) Weed hosts of novel carrot viruses (Warwick samples) Defra PhD studentship: The crop virome : - Virus ecology of carrot crops - CaTV: Characterisation and impact - Quantifying the effects of asymptomatic infection

14 Candidatus Liberibacter solanacearum The Zebra chip pathogen

15 Candidatus phytoplasma asteris Aster Yellows Phytoplasma SOURCE: Nisbet C, Ross S, Monger WA, Highet F, Jeffries C, First report of 'Candidatus Phytoplasma asteris' in commercial carrots in the United Kingdom. New Disease Reports 30, 16.

16 Acknowledgements This project was carried out with funding from HDC project FV 382 (a & b) Funding from Defra Plant Health Capability is supporting Zuri Rozado PhD studentship Howard Hinds (Root Crop Consultancy Ltd) Rodger Hobson (Hobson Farming Ltd) Fera staff in Virology, The Molecular Technology Unit and Applied Genomics team Andy Aspin (Bacteriology Fera)